In medical malpractice cases, the American as well as the German systems of law are faced with a basic dilemma: since liability is based on fault, the plaintiff who suffers bodily harm in the course of medical treatment often finds it very difficult to carry the burden of proof incumbent on him according to the normal rules of evidence. In most cases, he was harmed while unconscious or in ways not understandable to him because of his lack of knowledge in the area of medical science. Moreover, he frequently faces the reluctance of medical expert witnesses to testify about matters unfavorable to one of their professional colleagues. Therefore, American and German courts are trying to alleviate the plaintiff's burden of proof. The present study investigates these facilitations and queries whether they are still compatible with the system of fault liability.